Many gasoline and diesel cylinder head covers are isolated systems. The covers may be balanced between elastomeric isolator grommets and an elastomeric perimeter gasket. One approach to improve sealing capability is to increase the overall stiffness of the isolation system. However, increasing stiffness of the isolation system may increase Noise Vibration and Harshness (NVH) of the engine and/or cylinder head cover. Conversely, decreasing stiffness of the isolation system may increase the risk of oil leaks.
As one example compromise between sealing and stiffness, U.S. Pat. No. 6,691,667 to Salemeh discloses a casing cover having an acoustically decoupled stop. The casing cover has an axial extension having a peripheral edge profiled to receive a profiled elastomer seal having an edge surface for engaging a sealing surface of the engine block.
However, the inventors herein have recognized several issues with such an approach. As one example, the approach requires that a tension be maintained between the axial extension of the casing cover, and the engine block, compressing the profiled seal. This approach still allows a substantial avenue for NVH to be transmitted from the engine block to the casing.
Thus, in one example, the above issues may be addressed by a cylinder head cover for an internal combustion engine wherein the sealing function and the NVH isolation function may be decoupled from one another. The cylinder head cover may include a gasket having an elongate first gasket part and a flexible second gasket part sealingly coupled with the first gasket part along a length of the first gasket part. A bottom carrier may be configured to hold the first gasket part against a cylinder head for sealing engagement with the cylinder head. In addition a cover body may be configured to provide a covering surface sealingly coupled with the second gasket part at a spaced apart distance from the cylinder head.
The first gasket part may serve to seal the cylinder head cover at a juncture between the cylinder head and the bottom carrier. By coupling the cover body to a the second gasket part a distance from the first gasket part, the sealing function and the NVH isolation function may be separated, and may be individually optimized. In this way an efficient, and cost effective, structure may be provided.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.